Error: stack/package not found

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Hello, I have just added a new package to my workspace, but ROS can not see the package and give the error :

I know I have to source it, but I just do not know how... Error: stack/package not found#

Please do not refer me ROS tutorial page, especially the first or third tutorial :) I do not ask here before trying ros tutorials page or internet in the end :)

I need a step by step answer, not something go that tutorial or look that page.

Thanks